This invention relates to systems and methods for detecting eye disease.
Age-related macular degeneration (AMD) is the leading cause of blindness among people over the age of 50 in the western world. It is a bilateral, although asymmetric disease, and comes in two forms:
Dry or non-neovascular AMD is the more common and milder form of AMD, accounting for 85-90% of all AMD. The key identifier for dry AMD is small, round, white-yellow lesions in the macula. Vision loss associated with dry AMD is far less dramatic than in the case of wet AMD. There is currently no treatment available for dry AMD. It is estimated that as many as 14 million people suffer from dry AMD in the United States alone.
Wet AMD is less prevalent than the dry form, accounting for about 10-15% of AMD cases. The term wet denotes choroidal neovascularization (CNV), in which abnormal blood vessels develop beneath the retinal pigment epithelium (RPE) layer of the retina. Wet AMD is characterized by the development of choroidal angiogenesis which causes severe, and potentially rapid, visual deterioration. The visual distortion typically consists of perceiving straight lines as curved due to deformation of the retina in a region overlying the choroidal angiogenesis. The wet form accounts for about 60% of all cases of adult blindness in the United States. In the US alone there are 200,000 new cases of wet AMD every year and a total of 1.7 million blind people from AMD.
Treatment modalities for wet AMD include conventional treatments such as laser photocoagulation and newer treatment modalities such as PhotoDynamic therapy (PDT). Experimental treatments that are under current investigation include feeder vessel coagulation and Trans-pupillary ThermoTherapy (TTT). All these proven or experimental therapies may halt or slow progression of the disease only if detected at an early stage and will not reverse existing retinal damage. Therefore, early detection is crucial to prevent severe visual loss.
Since approximately 12% of dry AMD cases develop wet AMD and subsequent blindness within 10 years, a patient diagnosed with dry AMD must be routinely examined by an ophthalmologist once or twice a year, depending on the severity of his condition. The patient is usually also given a so-called xe2x80x9cAmsler gridxe2x80x9d for weekly self-examination at home for symptoms of wet AMD. The patient is advised to consult an ophthalmologist immediately in the event that symptoms are noticed. The Amsler grid and its modifications (such as the xe2x80x9cthreshold Amslerxe2x80x9d or the xe2x80x9cred Amslerxe2x80x9d) have been displayed to be poor detectors of early changes associated with wet AMD for several reasons. One is the phenomenon of xe2x80x9cfilling-inxe2x80x9d whereby the brain fills in missing parts in the pattern or corrects defects in the pattern. The subject thus fails to perceive a distorted pattern as being distorted. Another problem with the Amsler grid is the inability of patients to adequately fixate their vision on a fixed point while taking the test. The Amsler test also suffers from low compliance stemming from the non-interactive nature of the test.
The degree of visual deterioration is a function of the size of the lesion and its proximity to the fovea at the time of diagnosis. Although most lesions probably start outside the foveal area, 70% are already foveal and large ( greater than 1500 microns) at the time of diagnosis. It is therefore crucial to identify the lesions at the earliest possible stage, while they are still small and have not reached the fovea. It is known that 70% of lesions diagnosed as treatable become untreatable within less than three months, which indicates that the progression of the disease is relatively rapid. As many as 70-80% of patients with wet AMD are already ineligible for treatment when they first consult their ophthalmologist because the disease has progressed considerably. This is due to the poor validity of existing self-assessment methods for detecting an AMD-related lesion at an early stage, and the time lapsed between noticing the symptoms and seeing an ophthalmologist.
A reliable method for diagnosing wet AMD at the earliest possible stage, in conjunction with a referral system aimed at lowering the incidence of visual deterioration in this devastating disease, are imperative. If detected early, laser therapy to destroy the abnormal blood vessels may prevent additional vision loss. It is therefore crucial to detect the transition from dry to wet AMD as early as possible.
The present invention provides an eye test for detecting retinal lesions such as those associated with AMD or diabetes. The method involves showing a subject a first pattern displayed on a surface. The pattern may be, for example, one or more lines. The subject then fixates his vision on a point on the surface. The first pattern is hidden and a second pattern is displayed at a different location on the surface. The second pattern may be substantially identical to the first pattern, or the two patterns may be different. The subject is then asked to compare the second pattern and a predefined pattern. If the second pattern and the predefined pattern were identical, but the subject has perceived them to be different, this is indicative of a lesion of the retina. The subject indicates a region in the second pattern that appears to him to be different from the same region in the predefined pattern. The location of the lesion on the retina is determined from the location of the region in the second pattern on the surface relative to the point where the subject""s vision was fixated. If the second pattern and the predefined pattern were not identical, but the subject reports that the two patterns were identical, this would indicate that he is not responding reliably to the test. Thus, the second pattern may be obtained by modifying the predefined pattern to simulate the predefined pattern as perceived by a person with an eye disease. For example, the second pattern may be obtained from the predefined pattern by displacing a component of the predefined pattern, removing a component of the predefined pattern, blurring a component, or altering an optical property of a component of the predefined pattern, such as color or intensity. Such modified patterns may also be used to demonstrate to subjects various types of visual disturbances associated with retinal lesions.
Since the subject will spontaneously shift his vision to the second pattern within about 200 msec after it appears, the subject may additionally or alternatively be asked to indicate whether any motion occurred of part of the second pattern relative to other parts of the second pattern as he shifted his vision, and if so, where in the second pattern the motion occurred. For example, a segment of a line that appears curved when in the periphery of the subject""s field of vision may appear to straighten as the subject shifts his vision and brings the pattern into the center of his field of vision. This apparent movement at the particular location in the pattern as the subject shifts his vision is indicative of a retinal abnormality in the corresponding region of the retina.
The test is repeated several times, each time presenting the second pattern in a different region in the subject""s field of view. This allows a retinal abnormality to be mapped on the retina.
In a preferred embodiment, the method is performed by displaying the patterns on a monitor screen such as a computer monitor, television, or stand-alone device. In this embodiment, the subject can be made to fixate his vision on a point of the screen by having him bring a cursor to the point on the screen using any computer input device such as a computer mouse, a keyboard, joystick or touch-screen. This causes the first pattern to disappear from the screen and for the second pattern to appear. The patterns may consist of one or more broken lines consisting of a plurality of segments. The subject indicates a segment in the second pattern that appears different to him than the corresponding segment in the first pattern by bringing the cursor to the point and clicking the mouse. For example, if the first and second patterns are broken lines, and the subject perceives the first pattern as being straight, but perceives the second pattern as having one or more unaligned segments, the subject would click the unaligned segments with the mouse.
The results of the test are typically transmitted in real time over a communications network to a processor. The network may be a computer network such as the Internet, local and wide are networks such as LAN, WAN, or PAN. The network may also be a telephone network using a modem and TCP/IP connection. The processor that analyzes the subjects responses and generates a diagnosis of the subject""s condition. The diagnosis and a recommendation for follow-up or referral for prompt examination are then transmitted over the communication system to the subject and to his care provider. The subject""s compliance may be monitored regularly by the processor by storing in a memory the dates that the subject is to perform the test. Failure to perform the test on schedule results in a reminder being sent to the subject over the communication network or by telephone to perform the test. A notice may also be sent to the health care provider.
Thus, in its first aspect the invention provides a method for detecting eye disease in an individual, comprising steps of:
displaying to the individual a first pattern at a first location on a surface, the first pattern consisting of at least one point;
fixating the individual""s vision on a point in the first pattern;
hiding at least a portion of the first pattern;
displaying a second pattern to the individual at a second location on the surface so as to allow the individual to form a perceived image of the second pattern;
obtaining a comparison of the perceived image and a predefined pattern;
repeating the first step of displaying, the step of fixating, the step of hiding, the second step of displaying, and the step of obtaining a number of times; and
determining whether the individual has an eye disease based on the comparisons.
In its second aspect, the invention provides a system for detecting eye disease in an individual, comprising;
(a) a surface configured to display a first pattern to the individual, the pattern consisting of at least one point;
(b) a device for fixating the individual""s vision on a point in a pattern displayed on the surface and hiding the pattern after the individual""s vision has been fixated on the point; and
(c) a device for selecting a portion of a pattern displayed on the surface.
In its third aspect, the invention provides a program storage device readable by machine, tangibly embodying a program of instructions executable by the machine to perform method steps for detecting eye disease in an individual, comprising steps of:
displaying to the individual a first pattern at a first location on a surface, the first pattern consisting of at least one point;
determining when the individual""s vision is fixated on a point in the pattern;
hiding at least a portion of the first pattern upon the individual fixating his vision on a point in the first pattern;
displaying a second pattern to the individual at a second location on the surface so as to allow the individual to form a perceived image; and
obtaining a comparison of the perceived image and a predefined pattern;
In its fourth aspect, the invention provides a computer program product comprising a computer useable medium having computer readable program code embodied therein for detecting eye disease in an individual, the computer program product comprising:
computer readable program code for causing the computer to display a first pattern to the individual at a first location on a surface;
computer readable program code for causing the computer to determine when the individual""s vision is fixated on a point on the surface and for hiding at least a portion of the first pattern when the individual""s vision is fixated on the point;
computer readable program code for causing the computer to display a second pattern to the individual at a second location on the surface so as to allow the individual to form a perceived image of the second pattern and;
computer readable program code for causing the computer to obtain a comparison of the perceived image and the predefined pattern.